Second Generation Superconducting Filaments and Cable

Abstract

A high-temperature superconducting filament and cable, and a method for manufacturing same. The substrate used to grow the superconducting layer is removed, and the exfoliated superconducting layer is coated with a protective layer, and then sliced into narrow strips. The strips are thereafter encapsulated with a conductive metal to provide a high-temperature superconducting filament. The filaments may be bundled together to provide a high-temperature superconducting cable.

Description

BACKGROUND OF THE INVENTION[0001]The present invention relates to high-temperature superconducting yttrium-barium-copper-oxide filaments and cable, and to a process for manufacturing same via the exfoliation of a superconducting layer from an epitaxial substrate.[0002]The advent of second generation (2G) YBa2Cu3O7 (YBCO) wire technology has spawned impressive technological progress since the first meter of 2G wire was manufactured in 1995. Further developments in the field have been driven by existing and emerging applications, such as fault current limiters, transformers, and wind turbines. The second generation superconducting (2G) wires have record high upper critical field and critical temperature, potentially enabling design of high-temperature superconducting magnets, which could be cooled with inexpensive single-stage crycoolers. The core 2G wire technology can be described as a thin (<2 micron) YBCO layer deposited on a 50-100 micron thick metal substrate. FIG. 1 shows th...

AI Technical Summary

Benefits of technology

The present invention relates to a method for manufacturing a high-temperature superconducting cable from a 2G wire. The 2G wire includes a superconducting layer positioned upon a metal substrate. The method includes separating the superconducting layer from the metal substrate, slicing the separated layer into narrow strips, and encapsulating the strips with an electrically-conductive material. The cable includes a plurality of twisted filaments, each with a protective coating and at least one metallic stabilizing layer. The filaments are encapsulated in the absence of a buffer layer and in the absence of a superconductor substrate layer, resulting in both surfaces of the superconducting layer being in substantially equal electrical conduct with the electrically-conductive material surrounding it. The cable can be greater than 100 meters long and has a width between 1-2 mm. The filaments can be twisted to reduce magnetization loss, and the number of filaments can be between 1 and 100. The filaments can also be transposed to reduce electrical loss.

Problems solved by technology

The architecture associated with known commercially-available wires presents a number of problems, particularly when this architecture is used in magnet applications:i) The high aspect ratio (≈1:1000) contributes to the magnetization (AC) losses, which can be as great as 10's of J / m of wire.

This asymmetric nature of the conductor architecture contributes to the non-uniform conductor heating during a quench, which is known to causes de-lamination of the superconducting layer, and subsequent failure.iii) Tape 100 exhibits highly anisotropic mechanical properties.

Assembling a solenoid magnet from pancakes requires labor-intensive splicing of the individual pancakes via diagonal splices.v) The architecture of a 2G tape does not allow for a simple splicing of a multi-strand cable.

Since the specific heat and the coefficient of thermal conductivity of most materials become very low at cryogenic temperatures (due to the phonon freeze-out), even relatively small amount of heat can cause a significant temperature rise.

Thus, the ramping rate of the magnet is often limited by the overheating of the outer pancakes.

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